1. Technical Field
The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly to a semiconductor device including an electrical fuse or an antifuse, and a method of manufacturing such semiconductor device.
2. Related Art
Semiconductor devices that include a fuse are known in the art, in which disconnecting the fuse enables adjusting a value of a resistance employed in the semiconductor device, and isolating a defective element to substitute with a normal element.
Methods of disconnecting the fuse include laser irradiation on a point to be disconnected of the fuse. JP-A No. H11-297837 discloses a technique of solving the following problem arising in the fuse disconnected by the laser irradiation. With the ongoing micronization of the design rules with respect to the semiconductor devices, interconnects to be disconnected are becoming finer. Accordingly, a laser repair apparatus employed for disconnecting a fuse interconnect is required to offer higher positioning accuracy for the laser irradiation. However, employing a brand new apparatus for each product of a newer generation only leads to continuous increase in manufacturing cost. JP-A No. H11-297837 proposes, therefore, a circuit configuration including a plurality of interconnects to be disconnected for switching an internal circuit, to thereby switch the circuit once any of the plurality of interconnects is disconnected, as a method of surely disconnecting the fuse interconnect with a one-generation older laser repair apparatus of insufficient positioning accuracy. According to the literature, such configuration reduces imperfect switching of the circuit arising from defective disconnection due to a shift of the laser irradiation position on the interconnect to be disconnected.
Apart from such method of disconnecting the fuse by laser irradiation, a method of disconnecting the fuse with a current is also known, as disclosed in JP-A No. 2005-39220 and JP-A No. 2005-57186. JP-A No. 2005-39220 discloses a fuse that can be melted with a smaller current. In JP-A No. 2005-39220, the conductor constituting the fuse is shaped so as to be folded back a plurality of times.
FIG. 12 is a plan view showing the fuse disclosed in JP-A No. 2005-39220. According to FIG. 12, the fuse 1100 is folded back twice.
The fuse 1100 includes a current inlet terminal 1101 and a current outlet terminal 1102, and a first linear portion 1103, a second linear portion 1104, and a third linear portion 1113 between the terminals. The fuse 1100 further includes a first perpendicular connecting portion 1106 connecting the first linear portion 1103 and the second linear portion 1104, and a second perpendicular connecting portion 1107 connecting the third linear portion 1113 and the second linear portion 1104.
In the fuse 1100 thus configured, when a predetermined current runs from the current inlet terminal 1101 to the current outlet terminal 1102, heat generated in a hatched section 1108 outside the fuse 1100 is added to heat generated in a hatched section 1109 inside the fuse 1100, to thereby accelerate the fusing of the second linear portion 1104 interposed between the hatched section 1109. Thus, the fuse 1100 can be easily melted apart.
JP-A No. 2005-57186 discloses a fuse in which a point to be melted apart is surrounded by a plate, such that the heat generated at the disconnection point is detained or accumulated in the vicinity thereof.
In addition, JP-A No. 2004-214580 discloses a fuse layout including an interconnect electrode having a barrier metal layer constituted of a metal having a high melting point and a main interconnect metal layer. The layout includes a plurality of melting type fuse units connected in series and a plurality of fuse pads that supplies a current to each melting type fuse. In this layout, when at least one of the fuse units is disconnected, the entire layout becomes disconnected. Accordingly, imperfect disconnection can be significantly reduced.
As shown in FIG. 12, in the fuse that can be disconnected by a current (E fuse, hereinafter referred to as electrical fuse), supplying a predetermined current from the current inlet terminal 1101 to the current outlet terminal 1102 enables disconnecting the electrical fuse. The electrical fuse can be disconnected by applying a voltage to a point between the current inlet terminal and the current outlet terminal of the electrical fuse to be disconnected, and is hence free from the problem originating from the positioning accuracy incidental to the laser irradiation for disconnecting the fuse.
However, the present inventors have discovered that the electrical fuse may incur a new problem.